1. Field of the Invention
The present invention relates to a ceramic heater and a method for producing the same.
2. Description of the Related Art
A known ceramic heater used for heating a semiconductor wafer is a disc-shaped alumina sintered body in which a heater electrode is embedded. For example, PTL 1 discloses a method for obtaining a ceramic heater, the method including preparing two molded bodies obtained by molding a mixed powder of alumina and magnesium fluoride so as to have a predetermined shape, arranging, on one of the molded bodies, a paste which is to become a heater electrode, then stacking the other molded body, and conducting firing at a low firing temperature of 1,120° C. to 1,300° C. In the production process of a ceramic heater, in the case where high-temperature firing at 1,700° C. is conducted, when tungsten carbide (WC) is used as a paste, WC is sufficiently sintered and appropriate electrical properties of a heater electrode are obtained. In contrast, in the case where low-temperature firing at 1,120° C. to 1,300° C. is conducted, the following problems occur. When WC is used as a paste, detachment of particles significantly occurs and the electrical resistance cannot be measured. When a mixed powder of WC and alumina is used as a paste, densification of the resulting electrode does not sufficiently occur, and sufficient electrical properties are not obtained (Comparative Examples 21 and 22 of PTL 1). Under this circumstance, for example, a mixed powder of WC, Ni, and alumina is used as a paste in PTL 1.